The present invention relates to an apparatus for measuring the flying height of a magnetic head used in a magnetic disk apparatus.
In a magnetic disk apparatus, a magnetic disk forming a magnetic film on a disk-shaped substrate is used as a recording medium, and a magnetic head for recording and reproducing is disposed on the magnetic disk. While being stopped, the magnetic head is contacting with the magnetic disk, but when the magnetic disk is rotated at high speed when driving, the magnetic head is lifted by a negative pressure generating groove provided in a slider of the magnetic head so as to be in a non-contact state, and recording or reading is done while keeping a small flying height. Recently, for high density recording, the flying height of the magnetic head is required to be as small as 100 nm or less.
When manufacturing such magnetic disk apparatus, it is necessary to measure preliminarily if the flying height of the magnetic head is a specified value or not, and a measuring apparatus of flying height of magnetic head is used for this purpose.
In this apparatus, as shown in FIG. 1, instead of the original magnetic disk, a transparent disk 10 made of glass or the like is used, a magnetic head 20 to be measured is disposed at one side of this transparent disk 10, and light emitting means 11 and light detecting means 12 are provided at other side. Usually, the magnetic head 20 contacts with the transparent disk 10, and is lifted when the transparent disk 10 is rotated at high speed, and in this state an exit light 13 is emitted from the light emitting means 11 toward the magnetic head 20 through the transparent disk 10, this exit light 13 is reflected on a principal plane 10a of the magnetic head 20 side of the transparent disk 10, and this reflected light 14a and reflected light 14b from the magnetic head 20 are received in the light detecting means 12, and by making use of the interference by phase difference of both reflected lights 14a, 14b, the flying height h of the magnetic head 20 is measured.
In such magnetic head flying height measuring apparatus, although the magnetic head 20 is lifted during rotation, when starting or stopping rotation, the magnetic head 20 contacts and slides with the transparent disk 10 Accordingly, the glass-made transparent disk 10 is worn out excessively due to sliding with the magnetic head 20, and by using for about a week, it is hard to read the reflected light 14 due to flaw, and hence it must be replaced. It is hence not only bothersome but is also inferior in reliability of measured value.
Yet, since the glass-made transparent disk 10 is low in stiffness, it is likely to be deformed when rotating at high speed, and hence it was hard to form thinly to reduced weight.
Still more, by using the glass-made transparent disk 10, when the flying height h of the magnetic head 20 is reduced to scores of nm, the transparent disk 10 is charged with static electricity, and adverse effects are caused on the magnetic head 20. In particular, as the magnetic head 20 is advanced in density, it is changed from the ID (inductive) head to the MR (magnetic resistance) head, and this MR head is weak in static electricity, and is damaged by static electricity when the flying height h is 20 to 40 nm.